The invention relates to a method for the manufacture of a section for windows or doors having an external surface and an internal surface and at least one web which separates a chamber between the external and internal surfaces.
With windows and doors, it is generally desirable to achieve high thermal insulation and sound proofing. To do so, both the construction of the glass area and the design of the frame sections are of importance. The present invention relates specifically to the design of the sections used for this.
Hollow sections are known with thin-walled hard PVC webs. As a result of the chambers formed by the webs, air remains in the hollow section which has an insulating effect with regard to the abutting wall. The chambers are intended to effect thermal insulation from the outside with respect to the inside of the section. For window sections, for example, 3-chamber systems are usual; since very recently, high-quality window sections have been fitted with 4-chamber systems.
However, the fact is problematic that webs or the solid material of the webs allows thermal conduction between the chambers which is substantially higher than the thermal conduction of air. While higher thermal insulation could also be achieved through a plurality of chambers, the number of chambers which can be introduced into the section is limited by the external geometry and by further reinforcements made of steel to be introduced into the section. Furthermore, the introduction of further chambers incurs high costs so that the number of chambers should not be increased without limit for this reason, too.
A hollow section as described above is already known, for example, from EP 0 828 052 A2. It is already described there to introduce an insulation film into the correspondingly formed chambers in the section during the extrusion process of the hollow section. In this process, the insulation film stored on a reel is supplied through a corresponding opening in the extruder nozzle, whereby a non-positive connection is created between the soft plastic material and the insulation film.
In this process, in which the insulation film is drawn off a reel as a pre-fabricated material and supplied to the extruder forming the section, a sufficiently good welding may be possible with the section in the edge region of the insulation film thanks to the comparatively thin wall of the insulation film. With thicker films or thicker, wall-like webs, however, a secure welding is no longer ensured.
To remedy this, one could have the idea of connecting several extruder lines directly to a tool which, on the one hand, form the external covering for each section and, on the other hand, the web dividing the section. However, if both the external section portion and the web disposed on the inside of the section are formed in the tool, then the problem arises of a uniform cooling down of the extruded plastic even with comparatively low forming speeds. While a comparatively fast cooling down occurs in the outside section region, the heat from the inner web formed in the tool can only be dissipated insufficiently so that deformation and warping of the total section occur.
It is therefore the object of the invention to provide a method for the manufacture of a section for windows or doors in which sections for windows or doors of the type first described can be formed while achieving high forming speeds.
This object is solved in accordance with the invention beginning with a generic method by the combination with the features outlined below. In this, the following process steps are performed:
Extrusion of the at least one web with a first extruder line;
The at least partial cooling down of the at least one web exiting the extruder line;
Introduction of the at least one web into a tool for forming the section;
Formation of the section with an external and internal surface in the tool connected to a second extruder line; and
Welding of the at least one web to the section part forming the external or internal surface in the tool during its exit from the tool.
By means of the method in accordance with the invention, the web exiting the first extruder line can be cooled so far prior to its entrance into the tool in which the external or internal surface of the outside section part is formed as is required, on the one hand, for a good weld in the edge region of the at least one web without, however, having to accept the problems of insufficient heat dissipation.
By means of this method, the usual forming speeds of complex window or door sections of the type first described can be at least doubled.
Preferred aspects of the method in accordance with the invention are produced as described below. According to these, the at least one web can be heated by the tool to a temperature at which the web still possesses sufficiently high stability to be welded to the section.
Furthermore, the at least one web can advantageously consist of a foamed material. With this, increased thermal insulation can be achieved simply without having to introduce even further additional webs or chambers to the window section.
For reasons of stability, it may be desirable to cool down the at least one web so far that welding is only possible with difficulty. Particularly for this application, it is provided in accordance with another aspect of the method to heat the edge region of the at least one web along which the latter should be welded so far that a good weld capability is achieved between the section part forming the external or internal surface and the at least one web.
Furthermore, instead of the one or more webs, a more complex interior section can also be weldable to the section part forming the external or internal surface.